Amorphous and crystallized (Gd4Co3)100-xBx alloys for magnetic refrigerants working in the vicinity of 200 K

Crystallized Gd4Co3 alloy has shown promising magnetocaloric properties resulting from two successive magnetic-entropy changes of the hexagonal phase. In this work, magnetic (Gd4Co3)(100) B-x(x) (x = 0, 5, 10 and 15) amorphous ribbons were prepared by melt spinning. The onset crystallization temperatures T-x for the alloys with x = 0, 5, 10 and 15 were found to be about 560, 565, 575 and 585 K, respectively. The Ho4Co3-type hexagonal phase was obtained for crystallized ribbons after annealing. All the amorphous and crystalline alloys order ferromagnetically and undergo the second-order transition at their Curie temperatures. Under an applied field change from 0 to 5 T, the maximum value of (-Delta S-M) for (Gd4Co3)(100) B-x(x) amorphous alloys increased from 6.7 to 7.8 J kg (1) K (1) with increasing B content. Large values of the refrigerant capacity (RC) were also obtained. For the crystallized alloys, the maximum value of (-Delta S-M) decreased to 6.2-6.4 J kg (1) K (1). Large magnetic entropy change and RC value, negligible coercive force and hysteresis, as well as high stability enable the (Gd4Co3)(100) B-x(x) amorphous alloys competitive candidates for the magnetic refrigeration materials working in the vicinity of 200 K. (C) 2012 Elsevier B. V. All rights reserved.